[Relationship between the antileukemic activity of L-asparaginase and Asn level around leukemic cells].

OBJECTIVE: To study the antileukemic activity of L-asparaginase through determining the changes of 4 kinds of amino acids (Asn, Aspa, Glu and Gln) in cell culture medium. METHODS: Following L-Asp treatment with designed concentrations and duration, the IC50 (inhibitory concentration 50%) of 8 kinds of common leukemia cell lines (U937, HL-60, Jurkat, NB4, THP-1, Namalwa, Karpass299, K562) were determined by CCK-8 assay. The changes of the 4 kinds of amino acids mentioned above were detected by high performance liquid chromatography (HPLC). RESULTS: The asparagines in cell culture medium were rapidly exhausted when treated with 0.01 U/mL L-Asp for 4 hrs or 1 U/mL L-Asp for 5 minutes. There were significant differences in the sensitivities to L-Asp of different leukemia cell lines. The sensitivities to L-Asp of various cell lines were dose-dependent. Low concentration of L-Asp resulted in a low IC50 and the IC50 increased following the L-Asp concentration increased. CONCLUSIONS: Different leukemia cell lines have different sensitivities to L-Asp, suggesting that exhaustion of asparagines around leukemia cells could not reflect the treatment efficacy of L-Asp. L-Asp antileukemic activity is dose-dependent, which suggests the importance of high-dose L-Asp on childhood acute lymphoblastic leukemia.

Expansion and activation of granulocytic, myeloid-derived suppressor cells in childhood precursor B cell acute lymphoblastic leukemia.

Precursor B cell acute lymphoblastic leukemia (B-ALL) is a B cell-derived, malignant disorder with the highest incidence among children. In addition to the genetic abnormality, a dysregulated immune system also has an important role in the pathogenesis of B-ALL. Myeloid-derived suppressor cells (MDSCs) represent one of the key drivers in immune tolerance against tumor cells, including various solid tumors and hematologic malignancies. The role of MDSCs in B-ALL remains poorly understood. Here, we showed that the granulocytic (G)-MDSC population was significantly elevated in both the peripheral blood and BM of patients with B-ALL, when compared with age-matched healthy controls. G-MDSCs levels correlated positively with clinical therapeutic responses and B-ALL disease prognostic markers, including minimal residual disease, and the frequencies of CD20+ and blast cells. The immunosuppressive function of B-ALL-derived G-MDSCs was mediated through the production of reactive oxygen species and required direct cell-cell contact, with the potential participation of STAT3 signaling. Overall, the results of our study support accumulation and activation of G-MDSCs as a novel mechanism of immune evasion of tumor cells in patients with B-ALL and may be a new therapeutic target.

[Effects of hermap gene on p-STAT5 kinases in signal transduction pathway during erythroid differentiation].

OBJECTIVE: To study the effects of hermap gene on kinases in erythroid signal transduction pathway and investigate the mechanism of hermap on erythroid differentiation. METHODS: The K562 cells expressing hermap and hermap-siRNA respectively were established for up- and down-regulating the expression of hermap gene. These K562 cells were then induced by Ara-C to erythroid differentiation and analyzed at 0, 24, 48, 72 and 96 h, respectively, for cell morphology and biphenylamine staining positive cells, determination of CD235a, CD36, kinases p-STAT5, p-Akt, p-MAPK and p-c-JUN by FCM; and quantification of hermap gene and γ (Aγ,Gγ) globin gene by FQ-PCR. RESULTS: With up-regulating hermap gene and inducing by Ara-C, K562 cells were changing to low ratio of nucleus to cytoplasm, cytoplasm colour from basophilic to pinkish or amethyst tinge, increase of number of biphenylamine positive cells and expression of CD235a, CD36, γ (Aγ,Gγ) globin gene, hermap gene and p-STAT5 from 0 to 96 h. At 0, 24, 48, 72 and 96 h of culture, the positive rates of p-STAT5 cells were detected of 0.46%, 4.54%, 20.01%, 23.65% and 33.08%, respectively. This results demonstrated that there was a positive correlation between expression of p-STAT5 and hermap gene expression (P < 0.05). CONCLUSION: hermap gene can stimulate erythroid differentiation of Ara-C induced K562 cells mainly through JAK/STAT5 signal transduction pathway.

[Establishment of the cell line K562 with stable expression of hermap and hermap-siRNA].

In order to establish K562 line with stable expressions of hermap and hermap-siRNA, amplified hermap and hermap-siRNA were cloned into pEGFP-c1 and pRNAT to acquire hermap-pEGFP-c1 and hermap-siRNA-pRNAT, respectively. These two plasmids were electrotransferred into K562 cells, then were followed by culturing with G418. The result showed that the transfer rate of hermap-pEGFP-c1-K562 and hermap-siRNA-pRNAT-K562 plasmids were 10.0% and 9.3%, respectively. After selective culture by G418, these two cell lines were still able to express GFP. It is concluded that the eukaryotic expression plasmids containing hermap and hermap-siRNA have been successfully constructed, and the cell lines of hermap-K562 and hermap-siRNA-K562 are established, definitely contributing to further functional investigation on HERMAP and its interaction with other proteins.

[Relationship between asparagine synthetase expression level and cell sensitivity to L-asparaginase in human leukemic cell lines].

This study was purposed to explore the relationship between asparagine synthetase (AsnS) mRNA expression level and the sensitivity of leukemic cell lines to L-asparaginase. The AsnS mRNA expression level in 8 cell lines (Jurkat, HL-60, U937, NB4, THP-1, Namalwa, Karpas299 and K562) was determined by real-time quantitative PCR (RQ-PCR) based on fluorescence dye Eva Green before and after treatment with L-Asp, and the cell proliferation rates were analyzed by CCK-8 assay. The results showed that there was a significant disparity of AsnS expression level in 8 cell lines, and there were significant increases of AsnS expression level in cells co-cultured with L-Asp (p < 0.05). Of all these eight cell lines, cells sensitive to L-asparaginase had lower AsnS expression level and cells resistant to L-asparaginase had higher AsnS expression. U937 which was the most sensitive to L-asparaginase had the lowest AsnS expression level, while K562 was natural resistant to L-asparaginase and possessed of the highest AsnS level. It is concluded that the AsnS plays a critical role in regulating cellular biological behavior after depletion of asparagine, the AsnS mRNA expression level in cells reflects the sensitivity of cells to L-Asp. The results may imply the possibility for the use of L-asparaginase in leukemia with lower AsnS expression level.

[Interaction between mixed-lineage leukemia and Menin proteins].

The study was aimed to investigate the subcellular localization of mixed-lineage leukemia (MLL) and Menin proteins, and to explore the interaction between these two proteins. The recombinant eukaryotic cell expression vectors of pcDNA3.1-myc-MLL and pCMV-flag-Menin were constructed respectively, and transfected into the HEK293T cells. Immunofluorescence technique was used to observe the subcellular localization of the two proteins. Co-immunoprecipitation and Western blot methods were applied to evaluate the expression and interaction of the two proteins. The results showed that MLL and Menin proteins could be co-localized in cell nuclei, and the study of binding in vivo revealed that MLL protein could be detected in the immunoprecipitation complex of anti-FLAG, while Menin proteins could also be found in the immunoprecipitation complex of anti-MYC. It is concluded that MLL and Menin proteins co-localized in cell nuclei have same location and the interaction exists between MLL and Menin proteins.

[Effects of human ERMAP-siRNA on erythroid differentiation of K562 cells induced by Ara-C].

In order to investigate the potential role of human ERMAP gene in erythropoiesis, the ERMAP-dsDNA was designed, ERMAP-shRNA expressing plasmids was constructed, and ERMAP-shRNA/K562 cell was established. Cell morphology, biphenylamine staining, expression of cell surface antigens as well as quantitative level of human ERMAP gene were observed during K562 cells differentiating toward erythroid lineage induced by Ara-C. The results showed that at 72 hours after Ara-C treatment, ERMAP-shRNA/K562 cell size became large with increasing cytoplasm content. The percentage of biphenylamine positive cells increased from 1.17% to 2.04% (p < 0.05), but still lower than that in group K562 + Ara-C. The percentage of CD36(-)/CD235a(+) increased from 8.83% to 11.28%, CD36(+)/CD235a(+) increased from 1.23% to 2.64%, and CD36(+)/CD235a(-) increased from 0.59% to 1.47% respectively, which were all lower than that in group K562 + Ara-C at either time point. At the same time, the level of ERMAP expression increased slowly from 2.52 x 10(-3) to 4.53 x 10(-3), which was also significantly lower than that of group K562 + Ara-C. It is concluded that the ERMAP-shRNA inhibits the Ara-C-induced erythroid differentiation of K562 cells, which further suggests that there is relationship between hERMAP and erythroid differentiation and development.

[Expression of human ermap gene in umbilical cord blood mononuclear cells during differentiation and development towards erythroid lineage].

The aim of study was to explore the potential of human erythroid membrane associated protein (ERMAP) gene in erythroid cell differentiation and development, mononuclear cells (MNCs) were isolated from umbilical cord blood and induced to erythroid cell differentiation by SCF, IL-3 and EPO. The cell morphology was observed by using optical microscopy, the positive rate of cells was counted by biphenylamine staining and the ratios of CD36+/CD235a-, CD36+/CD235a+, CD36-/CD235a+ cells were detected by flow cytometry, the change of human ermap gene expression level was analyzed by using fluorescent quantitative PCR (FQ-PCR). The results showed that the ermap gene expression level increased while MNCs were induced to erythroid lineage after treatment with SCF, IL-3 and EPO. It is concluded that the human ermap gene plays an important role in differentiation and development of erythroid cells.

[Detection of minimal residual disease in children leukemia patients by using PCR - review].

MRD detection in children leukemia has a potential importance to predict clinical outcome and to modify treatment protocols of the diseases. Although some patients with leukemia have achieved complete remission according to the clinical and morphological criteria, there are still very low numbers of malignant cells that can not be discriminated by morphology and remained in bone marrow, which is called minimal residual disease (MRD) and is the main reason leading to relapse. MRD detection has an important significance for designing treatment protocols. Several methods of MRD detection have been developed. These include conventional cytogenetics, fluorescence in situ hybridization (FISH), flow-cytometric immunophenotyping (FCM), Southern blot and polymerase chain reaction (PCR) techniques, etc. Each of these techniques has its advantages and disadvantages, so not all of them are suitable for clinical MRD detection because of several inherent disadvantages, such as limited sensitivity, time-consuming, high cost, or requiring high-quality DNA or RNA. For example, the sensitivities of conventional cytogenetics, FISH, FCM and Southern blot approaches for MRD monitoring are 10(-1) - 10(-2), 10(-2), 10(-3) - 10(-4) and 10(-1), respectively. Relatively, PCR can reach a good sensitivity of 10(-4) - 10(-6), and show more advantages, such as fast, specific, simple and low-cost, as well as minimal amounts of DNA or RNA for detection, etc., so PCR has its specific features for MRD detection. In this review, the progress on the detection technique for screening leukemia specific marker by muitiplex PCR and FQ-PCR in recent years are summarized.

[Expression of human ERMAP gene in fetal tissues].

Human ERMAP (hERMAP) is a novel gene coding for erythroid membrane-associated protein, which may play a role in erythropoiesis. To explore the role of hERMAP in fetal hematopoiesis, 29 fetuses of inevitable abortion with the fetal ages of 9 - 36 weeks were collected, and the total RNAs were isolated from the liver, spleen, kidney, heart, lung, thymus, brain, bone marrow and skeletal muscle, the RNAs from which at 25(+5) week fetal age were used to detect hERMAP expressions in different fetal tissues with Northern blot, and the hERMAP in various fetal tissues were quantified by FQ-PCR. As a result, Northern blot showed that hERMAP was expressed in liver and bone marrow at 25(+5) fetal age, but not in the other organ tissues. FQ-PCR results indicated that the hERMAP had been still expressed in 9 - 36th week fetal liver, increased starting from 12th-week, reaching a peak between 18 - 20th week and declining slowly starting from 21st-week. In the fetal bone marrow, expression of the hERMAP began from 15th week, reached a highest level between 27 - 32nd week and fell rapidly from 33rd week, the expression level of which was lower than that in liver. The low level expression of this gene was observed in some specimens of kidney, heart, lung, thymus, brain and skeletal muscle. It is concluded that the expression of hERMAP in fetal liver approximately consistent with haematopoiesis of fetal liver, and the expression of this gene in bone marrow aged 15 - 32nd fetal weeks coincides with haematopoiesis of fetal bone marrow. It suggests that the function of the hERMAP is possibly related with the migration of erythroid cells to liver and bone marrow during the fetal development process.

[RNA isolation from human embryonic tissues].

To investigate the method of RNA isolation from human embryonic tissues and the factors influencing the quality of RNA, the RNA from human embryonic tissues obtained with drug-induced labor or non-drug induced labor were isolated by using grind with liquid nitrogen or homogenizer without liquid nitrogen. The results showed that the positive rates of RNA integrity in grind with liquid nitrogen group and in homogenizer without liquid nitrogen group were 68.42% and 29.79% respectively, and there was significant difference between these two groups; however, there was no statistic difference in positive rate of RNA integrity, OD(260)/OD(280) ratio and beta-actin gene expression level between the drug-induced labor group and non-drug induced labor group. It is concluded that pulverize of tissue in liquid nitrogen remains the integrity of RNA isolated and may be applied for RNA isolation from human embryonic tissues. The quality of RNA is not affected by different methods of induction of maternal labor.

[Study on the expression of human ERMAP gene in erythropoietic and macrophage differentiation of K562 cells].

In order to investigate the potential of human ERMAP gene in erythroid cell differentiation, K562 cells were induced to erythroid lineage by Ara-C and to macrophage lineage by TPA, human ERMAP mRNA was detected by fluorescent quantitative PCR. The results showed that human ERMAP mRNA increased while K562 cells were induced to erythroid lineage after treatment with Ara-C at 2.5 x 10(-6) mmol/L/L and 1.0 x 10(-6) mmol/L/L. Human ERMAP mRNA not changed while K562 cells were induced to macrophage lineage after treatment with TPA at 2.0 x 10(-6) mmol/L/L and 1.0 x 10(-6) mmol/L/L. It is concluded that human ERMAP gene plays an important role in differentiation and proliferation of erythroid cells.

[Expression of human ERMAP gene in different cell lines].

To investigate the pattern of human ERMAP gene expression in different cell lines, 15 cell lines derived from hematopoietic tumor, somatic tumor and normal tissue were chosen and were cultured; cells were harvested after culture for 12, 24, 36, 48, 60 and 72 hours; the expression of the human ERMAP was detected by using fluorescent quantitative PCR. The results showed that human ERMAP gene expression was positive in K562 cell line at interval of 12 and 24 hours, and the expression levels were (5.092 +/- 2.331) x 10(6) cps/microl RNA, (5.328 +/- 3.916) x 10(6) cps/microl RNA, respectively; ERMAP gene expression was also positive in ECV304 cell line at interval of 24 hours, and the expression level was (0.84 +/- 0.12) x 10(6) cps/microl RNA; and its expression was negative in other 13 cell lines. It is concluded that human ERMAP gene expression in ECV304 cell line was found first, and its expression in K562 cell line was further confirmed.